Go to Settings ‣ Discuss ‣ Incoming Mail Servers.

Configure the Incoming Mail Server and set Filters:

• Use "Reply-To" Header Matching to capture only responses to emails sent from Odoo.
• Use Custom Email Aliases (e.g., leads@yourcompany.com) to route emails properly.
• In the Lead/Opportunity Settings, set emails to be converted only if linked to an existing record.